This invention relates to a reflex exposure imaging member and, more particularly, to a reflex exposure imaging member having a particular composition as the photoconductive layer.
Xerography, as originally described in U.S. Pat. No. 2,297,691 to Carlson and later related patents, generally includes the steps of charging a photoconductive insulating member to sensitize it and then subjecting the photoconductive member to a light image or other pattern of activating electromagnetic radiation which serves to dissipate charge in radiation struck areas, thus leaving a charge pattern or latent electrostatic image on the photoconductor conforming to the radiation pattern. In most instances, the exposure step is made utilizing an expensive lens system. Following exposure, the image is developed by the deposition of electrostatically attractable, finely divided, colored material, referred to as toner, on the exposed photoconductor thereby forming a toner image corresponding to the latent electrostatic image. The toner image is subsequently transferred to a copy sheet which is generally plain paper.
Subsequent to the original contribution made by Carlson, a reflex type exposure technique was disclosed in several patents referred to hereinafter in the prior art section of this application. These reflex exposure methods have not become of commercial significance for several reasons. Initally, the structure of the photoconductive member was complex in order to achieve the required transparency necessary to render the imaging member operative. Secondly, because of the complex structure of the imaging member, it was difficult to clean the residual electrostatographic toner remaining thereon, after the completion of each cycle. Further, the images obtained by utilizing the reflex exposure technique as described in the patent literature are limited with regard to the maximum density of solid reproduced image areas. Thus, because of these problems, the xerographic industry progressed in directions other than by reflex exposure.
With the advent of organic photoconductive materials, some of which have varying degrees of transparency, reflex exposure techniques appear in a more favorable light because of the simplicity of structure which can be employed when considered in conjunction with the organic semi-transparent photoconductors. However, a problem which exists in the use of a reflex exposure technique is that a significantly longer exposure time is generally required in order to expose the photoconductive member significantly to thereby impose on its surface a latent image suitable for development. Thus, a photoconductive material which has varying degrees of transparency because of its inherent nature, cannot merely be utilized in an exposure of the reflex type because the sensitivity of these materials and the transparency thereof is not sufficient for establishing the latent image within the time frame suitable for this purpose.
Accordingly, it is the primary object of the present invention to provide an improved reflex exposure imaging member which overcomes the problems mentioned above.